com.google.errorprone.bugpatterns.MultipleTopLevelClasses Maven / Gradle / Ivy
/*
* Copyright 2015 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.LinkType.CUSTOM;
import static com.google.errorprone.BugPattern.SeverityLevel.SUGGESTION;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import com.google.common.base.Joiner;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.StandardTags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.CompilationUnitTreeMatcher;
import com.google.errorprone.matchers.Description;
import com.sun.source.tree.ClassTree;
import com.sun.source.tree.CompilationUnitTree;
import com.sun.source.tree.Tree;
import java.util.ArrayList;
import java.util.List;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
altNames = {"TopLevel"},
summary = "Source files should not contain multiple top-level class declarations",
severity = SUGGESTION,
documentSuppression = false,
linkType = CUSTOM,
tags = StandardTags.STYLE,
link = "https://google.github.io/styleguide/javaguide.html#s3.4.1-one-top-level-class")
public final class MultipleTopLevelClasses extends BugChecker
implements CompilationUnitTreeMatcher {
@Override
public Description matchCompilationUnit(CompilationUnitTree tree, VisitorState state) {
List names = new ArrayList<>();
for (Tree member : tree.getTypeDecls()) {
if (member instanceof ClassTree) {
ClassTree classMember = (ClassTree) member;
switch (classMember.getKind()) {
case CLASS:
case INTERFACE:
case ANNOTATION_TYPE:
case ENUM:
if (isSuppressed(classMember, state)) {
// If any top-level classes have @SuppressWarnings("TopLevel"), ignore
// this compilation unit. We can't rely on the normal suppression
// mechanism because the only enclosing element is the package declaration,
// and @SuppressWarnings can't be applied to packages.
return NO_MATCH;
}
names.add(classMember.getSimpleName().toString());
break;
default:
break;
}
}
}
if (names.size() <= 1) {
// this can happen with multiple type declarations if some of them are
// empty (e.g. ";" at the top level counts as an empty type decl)
return NO_MATCH;
}
String message =
String.format(
"Expected at most one top-level class declaration, instead found: %s",
Joiner.on(", ").join(names));
for (Tree typeDecl : tree.getTypeDecls()) {
state.reportMatch(buildDescription(typeDecl).setMessage(message).build());
}
return NO_MATCH;
}
}